Various types of gaskets are needed in cellular phones. Their purpose is to create acoustic sealing, to prevent dust from penetrating into the phone, to provide EMI-shielding etc.
The currently employed gaskets of the above mentioned type are made of soft elastic foam plastic and sealing is obtained when the gasket is compressed. To achieve an efficient sealing the compression of the gasket must be as large as possible, i.e. the uncompressed gasket must have a considerable thickness in order to obtain a tight sealing in its compressed state. However, it may be very difficult to assemble a phone with thick gaskets since the uncompressed gaskets interfere with the mating components and therefore require excessive force to be applied.
A gasket intended for use as a fluid seal in a plate and frame apparatus, such as a heat exchanger, is disclosed in U.S. Pat. No. 5,486,010. The gasket material comprises a core of elongated and preferably expanded polytetrafluoroethylene (PTFE) contained within a tight wrap of high strength film. The gasket is pre-compressed to aid installation by forming the gasket under pressure to the desired shape. However, the densification should not be so great that further compression and fitting of the gasket cannot occur during actual installation. Sealing is only obtained at the final compression when the plates are stacked in series and mounted between frames which then are tightened by means of compression bolts.